Howdy everyone. Recently picked up a 92 2.3 5 speed. It wasn't running, but all it needed to get back on the road was the eec relay. The CEL has been on since I've gotten it going.
The codes are (KOER)
116 - ECT out of range172 - O2 not switching, lean327 - EGR signal low411 - idle not proper179 - rich at part throttle (KOEO)
It has a new ECT and O2 sensor. I went ahead and replaced the O2 sensor with a known good one lying around, and still got the same codes. Haven't replaced the ECT yet. Don't wanna throw parts at it.
​​​​​I pulled my test wire out of the eec test connector to clear the codes. Upon startup, the cel came right back on like normal. I decided to pull the battery terminals for 30 minutes. Again, on start up the light came right back on!
After doing some research I thought maybe the computer capacitors were bad. Pulled the pcm apart and what do you know they look just fine. No bulging, no leaking.
At this point I'm pretty much stumped. Is it possible there is just something wrong with the circuitry in the computer?
Thank you to anyone who responds.

 

Welcome to the forum

Unlikely to be the computer, but possible

If truck was sitting for awhile, whats the fuel like?
Gasoline only last for about 6 months in a gas tank unless its filled to the top so little or no air exposure

I thought 1992 would have 2 digit codes, 1993/4 were 3 digit OBD1

But no matter
ETC sensor is new?
Test the wires
Unhooked, one wire should show 5volt with key on, this wire is shared by most sensors so would expect other sensor codes if the 5v power from computer was the issue but could just be the 5v wire at the ECT that's the issue
With OHM meter you can test the sensor itself, graph for temp here: https://www.explorerforum.com/forums...jpg?1583516355

Colder temp is higher OHMs, at 70deg should see about 37k ohms, cold engine of course, lol
If engine is fully warmed up then 3k ohms, about 185degF

If sensor tests as OK then its most likely a wiring issue back to computer
Pin 26 on computer is the 5volts that runs out to all the sensors
Pin 7 is the "return" voltage from ECT that computer uses for "temp"

And O2 could also be wiring issue
O2s generate their own voltage, 0.1v to 0.9volt, but only after they are heated up above 650degF by exhaust and their built in heaters
0.1v is called "lean"
0.9v is called "rich"
Neither has to do with fuel, lol, lean means high oxygen, rich is low oxygen, O2 can ONLY see Oxygen, not fuel
Computer expects to see 0.3, to 0.5v if all is well

If an O2 sensor wire was broken then computer would see 0.0v from O2 so for the computer that's 172 Oxygen sensor not switching - system is or was lean
Voltage is not changing and its 0.0v so lean
There is no broken wire codes, so its the only code computer can use, the no switch(changing volts) is the tell tale usually(assumes engine is not pinging/knocking really bad)

Also check fuses, the O2 sensor heater has as fuse in the engine or cab fuse box, it can also cause "no switching" if its blown
Computer pins 29 and 49 are for the O2's two wires

179 (M) Fuel system was rich at part throttle
Never actually seen this code in person, so not sure what to make of it, with the "lean" no switching code
Are BOTH codes still present after the reboot?